The study documents a 10 percent falloff in central line-associated bloodstream infections in Illinois during the first six months of 2009, when compared with the number expected based on data from 2006 to 2008.

But Vermont's infections plunged more than 70 percent, Oklahoma's by 50 percent and New Hampshire's by more than 40 percent, the CDC reported.

The government study is the first to publish state-by-state data for these infections, called CLABSIs, which kill up to 31,000 people in hospitals each year. Research over the past several years has demonstrated that the infections are largely preventable.

They occur when bacteria or other pathogens enter a patient's body at the site of a central line — a large catheter usually implanted in a blood vessel in a patient's neck or chest. The catheters are used to administer fluids and medication.

Seventeen states, including Illinois, require that hospitals report data about CLABSIs to the National Healthcare Safety Network, operated by the CDC. Adjustments are made to account for differences in the type of data submitted, a CDC official said. For instance, Pennsylvania mandates that infections be reported from all units within a hospital. Other states, such as Illinois, require reporting only from intensive care units.

The new CDC report puts Illinois 12th among the 17 states in terms of the ratio between the number of CLABSIs that actually occurred versus those that were expected. Maryland came up last with 30 percent more infections than expected. South Carolina had 16 percent more.

Government officials emphasized the purpose of the report wasn't to compare states but to enable them to measure progress in combating infections.

States that audit data submitted by hospitals tend to report more infections, officials noted. Maryland audits hospital data; Illinois plans to start doing so later this year, according to Melaney Arnold, a spokeswoman for the Illinois Department of Public Health.

Meanwhile, Illinois is already tracking CLABSIs closely and making more comprehensive infection data available. The Public Health Department has published infection data for more than 140 hospitals across the state, highlighting institutions that have excessively high rates of CLABSIs and those that have brought the medical complications under control.

The federal analysis supports findings from the state report. It shows that half of hospitals in Illinois had 64 percent fewer infections than expected. But 10 percent of hospitals had infection rates nearly 200 percent higher than expected, skewing Illinois' overall performance.

Nationally, 1,538 hospitals in 47 states and Washington, D.C., report data about CLABSIs to the CDC. Infection rates dropped 18 percent among these institutions in the first half of 2009.

The reduction shows that "care in hospitals is getting safer but we know that there is more work to be done," said Dr. Arjun Srinivasan, associate director for the CDC's healthcare-associated infection prevention program.